An election was held among the production and maintenance employees of Wyman-Gordon (C) to select one of two labor unions as their exclusive bargaining representative, or to choose not to be represented by a union at all. The Board ordered C to furnish a list of the names and addresses of its employees who could vote in the election. C refused to comply. Both unions were defeated in the election. The Unions protested this result and the Board upheld their objections because C had failed to provide the required lists. A new election was ordered. C refused to obey the Board again. The Board issued a subpoena ordering C to provide the lists. The Board then filed an action in the U.S. District Court seeking to have its subpoena enforced or to have a mandatory injunction issued to compel C to comply with its order. The district court agreed. The court of appeals reversed holding that the Board's order was invalid.